1. Field of the Invention
The present invention relates to a bidirectional transceiver module and more particularly, to a COB package type bi-directional transceiver module, which has the photo diode bonded to the printed circuit board by COB (chip on board) package and the laser diode installed by means of TO package.
2. Description of the Related Art
A bi-directional WDM (wavelength division multiplexer) transceiver module is capable of transmitting and receiving two light sources of different wavelengths (1550/1330 nm) through a SMF (Single Mode Fiber), achieving bi-directional transmission operation. This bi-directional transmission design increases the use of the bandwidth of a fiber. In comparison to the design of conventional bi-directional fiber optic transmission modules, this bi-directional transmission design saves one fiber optic, minimizes module size, and increases the use of bandwidth in high density main distribution facility room.
FIG. 1 is a schematic drawing of a bi-directional WDM transceiver module according to the prior art. According to this design, the bi-directional WDM transceiver module comprises a laser diode 11, a photo diode 12, a WDM (wavelength division multiplexer) 13, a filter 14, and a module housing 17 houses the members. The bi-directional WDM transceiver module is connectable to a SMF (Single Mode Fiber) 16 through a fiber optic connector 15 (for example, a receptacle, pigtail, or the like) for bi-directional transmission of signal. The bi-directional WDM transceiver module uses the laser diode 11 as light source that receives electric signal from driver and converts the signal into optical signal of wavelength λ1 (for example, 1550 nm) for transmission. The bi-directional WDM transceiver module uses the photo diode 12 as photosensitive means to receive optical signal of wavelength λ2 (for example, 1310 nm) and to convert the signal into an electric signal, for enabling the electric signal to be amplified by a TIA (Transimpedance Amplifier) for output. The WDM 13 is adapted to separate the light sources of wavelength λ1 and wavelength λ2, for enabling optical signal of λ1 from laser diode 11 to pass through WDM 13 to the SMF 16 for output. Optical signal of λ2 from SMF 16 is reflected onto the filter 14 by the WDM 13 and then sent received by the photo diode 12. Therefore, the bi-directional WDM transceiver module achieves bi-directional transmission operation.
The manufacturing of the aforesaid prior art bi-directional WDM transceiver module is started from the laser diode 11 which is housed in a TO package, and then the ferrule of the fiber optic connector 15 is aligned to the laser diode 11 and welded on the module housing 17, and then the photo diode 12, which is also housed in a TO package, and the other components are mounted in the module housing 17, completing OSA (Optical Sub-assembly) manufacturing process, forming a structure of bi-directional transceiver as shown in FIG. 2. During the manufacturing process of the bi-directional transceiver, the LD adopts TO packaging, and the photo diode can also adopts TO packaging.
In order to satisfy heavy bandwidth requirement for telecommunication and network, optical communication networks will become more and more popular in city areas. However, due to limited land space and heavy rent for office in city areas, there is a limitation to the expansion of trucking space. Therefore, it is important to provide more number of transmission ports with same size of telecommunication and network facility. The most effective and direct way to solve the problem is to reduce the size of the bi-directional transceiver so that more transmission ports can be provided in a limited space.